抄録
Initial stage of processes and energy bandgap formation in nitridation of silicon surfaces using nitrogen radicals have been studied. According to scanning tunneling microscopy observations and scanning tunneling spectroscopy measurements, at the initial stage of nitridation, linear defects perpendicular to dimmer rows were formed to coincide with an initial nitridation reaction preferentially at backbonds of surface Si atoms. After the nitride formation, the surface roughness depends only on substrate temperature regardless of radio frequency (RF) power, which means that the growth mode of nitrides is attributed to the surface migration. Contrary, the energy bandgap of silicon nitrides is significantly affected by not only substrate temperature but also RF power. Absorption and emission spectroscopy results suggest that the contribution of the excited-state nitrogen atoms to the nitridation increases with increasing the RF power. Control of surface migration and radical species is crucial to form the monolayer-thick nitride layer with both an atomically flat surface and a wide energy bandgap.